Biostatistics PhD student, UC Berkeley

Let me just start by saying this: if you're in the business of visualizing data, ggplot2 is great. There's a bit of a learning curve, especially for those new to R — but it's pretty redeeming when you finally master it and people actually want to look at your graphics. These days — partly for aesthetics and consistency, but also partly out of pure stubbornness — I try to create all of my plots with ggplot.